Greases used for lubricating bearings often have a shorter service life than the expected service life for the bearings lubricated thereby. For that reason rolling bearings have to be relubricated, and relubrication shall take place at a time when the condition of the lubricant is still satisfactory.
The requirement for relubrication depends on many related factors, including bearing type and size, speed at which the bearings are running, operating temperature, type of grease, bearing environment, etcetera.
The common method for deciding the relubrication intervals t.sub.f for bearings is by using statistical rules, where for instance the SKF recommended relubrication intervals are defined as the time period, at the end of which 99% of the bearings are still reliably lubricated.
Diagrams have been created which are used for establishing the relubrication interval for a specific bearing, at a speed factor “A” multiplied by the relevant bearing factor “bf”, where the graphs represent the load ratio C/P. Such a relubrication interval chart can be seen in the accompanying FIG. 1. For a bearing having a value of Ab.sub.f<<475000 and a C/P ratio=8, it can be seen that the calculated t.sub.f value will be 1000 operating hours.
With this earlier and commonly used method, it is possible to decide before the operation of the bearing assembly or bearing assemblies shall be relubricated, and the method has proven itself to give a fairly satisfactory and reliable result.
However, some of the factors to be considered may change gradually during operation for the bearing assembly or bearing assemblies relubricated by the automated lubrication system.
Thus it is possible that the load acting on a bearing can change, the temperature, at which the bearing is operating, can vary for external reasons and the rotational speed can be altered. The previous method of setting the t.sub.f value described above, thus will only give a surely satisfactory result under the prerequisite, that all parameters or factors used at the original setting of the relubrication interval are maintained unchanged.